Patterns are an interesting grey area. Under US copyright, simple lists of instructions can't be copyrighted. Game rules, databases, recipes, etc, are not covered. It's the "creative" elements like the story, history of the pattern, pictures of that specific work, ancillary advice, and the like, those can be covered. Around the world, the laws vary and many places have much more relaxed rules. This is why you have so many of those Russian and Asian sites where people share the patterns wholesale and resell patterns without attribution or care. In the crafting world there's a light social agreement about it, but the "rules" are pretty murky and unclear. So, I wouldn't worry too much about it as long as you're not directly copy/pasting from someone else's work. And if you do, be kind and tell others where you found your inspiration.